User interaction with computers continues to increase each day. More jobs require individuals to interact with computers and more people are choosing to interact with computers for both work and entertainment. Various tracking devices for interacting with a computer include electronic mice, keyboards, joysticks, and touch pads. Along with the proliferation of various computing devices for work and entertainment has come the concomitant proliferation of various tracking devices. Other tracking devices, including electronic pens or styluses, personal digital assistants (PDAs), cellular telephones, remote controls and other computing devices, thus have evolved to allow users to interact with different computers and computer systems, sometimes in a specialized manner. For instance, electronic pens or styluses give a user the precision with an input device, to capture and translate pen strokes as input to a host device, in a manner that preserves the integrity of the movement of the pen or stylus to sufficient degree of detail such that the user may draw illustrations, draft letters or notes with handwriting, or perform operations in connection with any other host applications that make special use of the enhanced input characteristics of the electronic pen or stylus.
Tracking devices generally fall into one of two types of systems: relative tracking systems or absolute tracking systems. A relative tracking system has the ability to discern relative motion from one position to another, independent of knowledge of absolute position. Methods of relative optical tracking include image correlation, differential pattern gradient based, laser speckle based and Doppler-based among others. One feature of a relative tracking system is that one or more sensors detect signals that change over time and can be processed in various ways to determine changes in relative position. An absolute tracking system has the ability to discern a position of the device irrespective of a previous determination. Electronic pens, for instance, commonly implement absolute tracking systems, and input devices generally implement one or the other, but not both relative and absolute tracking systems. Cost, size, and difficulty in combing the two from a technological standpoint have left manufactures choosing from one of the two methods when constructing their respective devices, though some pens may include both types of systems. For instance, commonly assigned copending U.S. patent application Ser. No. 10/891,484, entitled “Methods and Apparatuses for Compound Tracking Systems,” filed Jul. 15, 2004 describes such a system.
As the use of pens becomes more ubiquitous with PCs, laptops, handheld devices such as PDAs, and other mobile devices, the number of computing device scenarios that require a user to bring a pen along with the computing device has also increased. Currently, for instance, a traveler may need to carry both a pen and a mouse on a business trip. Precious space is required to carry each device so the user may decide not to carry one or both. Consequently, in order to make a pen more appealing to a customer, it would be desirable to increase the functionality of the pen beyond its computing device input tracking functionality. It would be further desirable if the pen could be used as both a pen and as a traditional mouse pointer device. It would be still further desirable to allow a user to simply switch between two modes corresponding to the mouse functionality of the pen device and the ordinary operation of the pen device, such as allowing a user to switch simply between ordinary pen mode-and mouse mode. If such a device was available, the customer would only need to carry a single device.